1. Field
The present disclosure relates to an image forming apparatus. More particularly, the present disclosure relates to an image forming apparatus that may be distributed in a state that a charging roller thereof is spaced apart from an image carrier thereof.
2. Description of the Related Art
Generally, electro-photographic image forming apparatuses, such as laser printers, facsimile machines, copy machines, composite apparatuses or the like, form a predetermined electrostatic latent image on an image carrier. After that, the image forming apparatus develops the electrostatic latent image on the image carrier with developer, transfers a developer image onto a printing medium and fuses the developer image onto the printing medium, thereby performing a printing.
The image forming apparatus includes an image carrier, an outer circumferential surface of which is evenly charged by a charging member, an exposure unit that emits light to the image carrier to form an electrostatic latent image, and a developing member that supplies developer to the image carrier to develop the electrostatic latent image into a developer image.
A method of evenly charging the outer circumferential surface of the image carrier through the charging member may be classified into a corona discharging method and a close charging method. The close charging method is a method of allowing a roller or a blade to be in contact with the image carrier and generating electric discharges in infinitesimal gaps between the image carrier and the roller or the blade to charge the image carrier. The corona discharge method has a problem that ozone is generated during ionization of the air. Therefore, at present, the close discharging method is widely used.
Specially, a roller contact charging method that is similar to the close discharging method is widely used. The roller contact discharging method is a method of causing a charging roller to be in contact with the image carrier with a predetermined pressure to charge the outer circumferential surface of the image carrier.
If the charging roller has prolonged contact with the image carrier under a predetermined pressure, quality problems such as compression set, migration, and the like, may occur in the charging roller. The compression set refers to a phenomenon that a contact portion of the charging roller which is in contact with, and is pressed by, the image carrier for an extended period of time is not restored to its original state. The migration refers to a phenomenon that substances contained in the charging roller come out of the charging roller, and are transferred to, and adhered onto, the image carrier due to heat and pressure generated by prolonged contact between the charging roller and the image carrier.
If the above-described phenomenon occurs, when a user prints output, horizontal stripes are formed on the printed image at a rotation cycle of the charging roller and/or at a rotation cycle of the outer circumferential surface of the image carrier to cause a poor image. To prevent this phenomenon, while the image forming apparatus is being distributed for sale after manufacture, the charging roller and the image carrier should not be kept in contact with each other.
To keep the charging roller and the image carrier spaced apart from each other during distribution, a special spacing member may be inserted between the charging roller and the image carrier to maintain therebetween a non-contact state, and then, the image forming apparatus having the special spacing member may be distributed. Thus, after buying the image forming apparatus, a user removes the special spacing member from a developing cartridge, mounts the developing cartridge into a main body of the image forming apparatus, and uses the image forming apparatus to print. However, this method may solve the migration problem, but may not solve the compression set problem. Also, this method has an inconvenience in that the user removes the special spacing member.
Alternatively, the charging roller may be configured to be spaced apart from the image carrier by spacing members disposed at opposite ends of the charging roller. In this case, when the image carrier is driven, the spacing members are rotated so that the charging roller and the image carrier are automatically in contact with each other. However, since this method needs a specific jig to cause a projection of the spacing member to face the image carrier, a manufacturing process is complex. Also, during distribution, due to impact or vibration the spacing member rotates by itself so that the charging roller comes in contact with the image carrier.
Accordingly, there is a need to provide an image forming apparatus that may prevent chemical and physical deformation from being generated in a contact portion between the image carrier and the charging roller due to leaving the image forming apparatus alone for an extended period of time and a variety of different temperatures and humidity environments during distribution.